Method of making a mount structure for flash lamps



July 31, 1962 R. M. ANDERSON 3,046,770

METHOD OF MAKINGA MOUN STRUCTURE FOR FLASH LAMPS Filed Nov. 12, 1959 Invervtor Rober' t: M. Anderson it) His llnited rates latent Bfidfifilfi Patented July 31, 1962 3,tl46,770 METHOD OF MAKING A MOUNT STRUCTURE FOR FLASH LAMKS Robert M. Anderson, Euclid, Ohio, assignor to General Electric Compare a corporation of New York Filed Nov. 12, 1959, Ser. No. 852,552 1 Claim. {61. 6731) My invention relates to photographic flash lamps of the type comprising a sealed bulb or envelope containing a combustion-supporting atmosphere and a loosely arranged filling of metallic combustible material which is ignited by an ignition means comprising a fulrninating primer and a filament or heater element adapted to set oil the primer. More particularly, my invention relates to the method of manufacture of the ignition means for such type flash lamps.

Conventional type flash lamps in common use at present are provided with ignition means customarily comprising a filament consisting of a short straight length of fine tungsten Wire, usually having an effective lighted length of the order of 50 to 65 mils, which is connected substantially straight across the inner ends of a pair of generally side-by-side lead-in Wires sealed into one end of the bulb. The filament is energized and heated, usually by a dry cell battery connected across the lead-in wires, to thereby ignite a fulminating primer coated on the inner ends of the lead-in Wires at their connections or junctions with the filament. The ignited primer then ignites, in turn, a filling of fdamentary metallic combustible material the ensuing combustion of which then produces a momentary flash of light of high intensity.

The assembly of the filament, its supporting lead-in wires, and the primer coatings on the inner ends of the lead-in wires, together comprise What is commonly known as the mount structure of the larnp. In the manufacture of the lamp, the mount structure is sealed into the bulb in a position in which the filament and the associated primer coatings or beads are located Within the filling of combustible material in the bulb so as to be more or less surrounded thereby and thus in effective ignition range relative thereto. To this end, it is the general practice to first introduce the combustible filling material into and distribute it within the bulb and to then insert the lamp mount, filament end first, into the open neck end of the bulb and into sealing position therein, with the filament and primer coatings of the mount located Within the filling of combustible material. With such procedure, however, because of the comparatively appreciable spacing between the primer coatings or beads on the lead-in wires of flash lamps as conventionally made heretofore, and also the substantially taut condition of the ignition filament between the primer beads, some of the strands of the filamentary combustible filling material Within the lamp bulb are usually trapped in and enter the space between the primer beads or coatings during the insertion of the mount into the bulb, and come in contact with and firmly press against the substantially taut ignition filament which extends more or less straight across the opening between the two primer beads. The strands of combustible material thus in contact with the taut filament then exert a cooling effect thereon during the energization and heating of the filament to set oil the primer. This cooling effect on the filament is sufiicient in some cases, as when the dry cell batteries are weak or the circuit contacts are poor, to prevent the filament from attaining a temperature high enough to ignite the primer, with the result that the lamp fails to flash. The flashability of the lamp thus is adversely affected by the contact of the ignition filament with the combustible material present Within the lamp bulb.

Moreover, the pressure of the combustible material against the fine tungsten wire filament with which it is in contact is also apt to cause elongation of the filament during the time it is heating up. The resulting reduction in the cross-sectional area of the filament, and the corresponding increase in its electrical resistance at the region of reduced cross-sectional area, therefore tends to cause either the burn-out of the filament at such region of reduced cross-sectional area, or a severing or pulling apart of the filament at such region, so that the lamp again fails to flash.

It is an object, therefore, of my invention to provide a method of making a mount structure for use in a flash lamp of the above mentioned character having improved flashability characteristics and greater freedom from filament burn-out, from lamp to lamp.

Another object of my invention is to provide a flash lamp of the above mentioned character having an ignition filament located Within but uniformly out of firm contact with the filamentary combustible material, from lamp to lamp.

Still another object of my invention is to provide a flash lamp of the above mentioned character having a lamp ignition mount structure of such a construction as to prevent firm contact of the ignition filament with the surrounding filamentary combustible material within the lamp bulb in substantially all cases.

A further object of my invention is to provide a novel method of making a flash lamp of the above mentioned character so as to eifectively prevent the filamentary combustible material from firmly contacting the ignition filament positioned therewithin.

Briefly stated, in accordance with one aspect of my invention, the primer-coated inner ends of the lead-in wires of conventional type lamp ignition mounts such as have been customarily used heretofore in flash lamps, across which lead-in who ends the ignition filament is connected in a substantially taut condition, are bent toward one another, prior to the insertion of the mount into the lamp bulb for sealing thereinto, until the primer coatings or beads of the mount practically touch one another, thereby not only materially decreasing the space between the primer beads so as to minimize the chance of entrance of the filamentary combustible material thereinto and into contact with the ignition filament, but also forming the taut filament into an open loop shape between the primer beads so as to have an appreciable amount of slack therein and thus be readily displaceable, in the event it should be actually contacted by the combustible material, whereby to obviate firm pressure contact therebetween in the completed lamp.

Further obg'ects and advantages of my invention will appear from the following detailed description of a species thereof and from the accompanying drawing.

In the drawing, FIG. 1 is an elevation of a flash lamp comprising my invention, and

FlG. 2 is a fragmentary elevation, on a greatly enlarged scale, of the ignition means or mount structure of the flash lamp comprising my invention.

Referring-to the drawing, the flash lamp there shown comprises a sealed light-transmissive envelope or bulb 1 which may be formed of glass and contains a filling of a combustion-supporting gas such as oxygen and a loosely arranged filling of filamentary metallic combustible material 2 of a composition such as zirconium, aluminum or aluminummagnesium alloy which is of a readily combustible character when in a finely divided or filamentary state. As shown, the combustible material 2 may be in the form of fine wire, ribbon, or other filamentary character such as that commonly known as shredded foil, the individual strands of the filamentary material having a crosssectional area of the order of one square mil.

Sealed into the neck end 3 of the envelope or bulb 1 is a lamp ignition means or mount structure 4 comprising a glass stem tube 5 extending into the envelope or bulb 1 and terminating at its inner end in a flattened stem press portion-6 through which are sea-led a pair of lead-in wires tions to the lead-in wires, of approximately 55 to 60 mils tact 10 and the side shell contact 11 of a conventional type lamp base 12 suitably secured to the neck and 3 of the envelope, as by the conventional basing cement (not shown). The envelope or bulb '1 may be exhausted and filledwith oxygen or other combustion-supporting gas in the conventional manner through an exhaust tube 13 extending from the stem press '6 of the lamp mount 4 and communicating with the-interior of the envelope through a side aperture 14 in the stem press. After evacuation of the envelope 1 and the introduction of the gas filling thereinto, the exhaust tube 13 is tipped-01f in the well.

known manner to thereby hermetically seal the envelope. So far as known, the primer-carrying inner ends or tips of the lead-in wires of prior type flash lamps have all been spaced an appreciable distance apart as compared to the cross-sectional size (around 1 square mil or so) of the individual strands of the combustible material 2, the lead tip spacing a (FIG. 2) ordinarily amounting to at least 50 mils between the inner facing sides of the wires. in addition, the ignition filaments of such lamps have all been connectedfsubstantially straight across the said lead tips' or inner ends of the lead-in Wires so as to be practically taut therebetween; Thus, in the commercial designated No. 5 flash lamp, for example, manufactured by applicants assignee, the inner lead tip spacing a has customarily amounted to approximately 55 mils, and the efl'ectiveor lighted length of the filament (i.e-., the length thereof between its connections to the inner lead tips) hasamounted to around 58 mils, the inner lead tip spacing customarily being made a few mils, i.e., 3 mils or so, shorter than the desired lighted length of the filament in order to provide a slight amount of slack in the filament for the purpose of insuring against tensioning and resultant breakage of the fragile filament by tensile forces that otherwise may be applied. thereto by the lead-in wires as, for instance, by their vibration during the handling or shipment of the lamps. Moreover, the primer coatings on the lead tips of prior type flash lamps have all been of such a thickness, usually amounting to around 5 mils or less in coating thickness, to produce a spacing lftherebetween at their inner facing sides of at least 40 mils, which distance obviously is comparatively large compared to the usual 1 mil or so cross-sectional size of the strands of combustible material 2.

'Because of such customary relatively wide spacing of the primer coatings or heads 9 in prior type flash lamps, therefore, there is considerable likelihood of some of the strands of the combustible filling material 2 in the lamp bulb becoming trapped between the primer coatings or beads9 and coming into contact with the substantially taut ignition filament extending therebetween, during the insertion of the lamp mount 4 into the lamp bulb for Lit sealing thereinto. The strands of combustible material thus in contact with the ignition filament are not only likely to exert a cooling effect thereon such as to in some 7 cases prevent the filament from heating to a temperature suflicient to set oif the primer, thus impairing the flashability of the lamp, but they also may act to apply sufficient tension to the substantially taut filament to in some instances result in elongation thereof and corresponding reduction in its cross-sectional area such as to cause'either the burn-out of the filament or a severing or pulling apart thereof, thus rendering the lamp inoperative.

In accordance with the invention, to prevent or minimize as much as possible the entry of any strands of the combustible material 2 into the space between the primer beads 9 and into firm contact with the ignition filament 8 extending therebetween, during the insertion of the lamp mount 4 into the bulb 1 for sealing thereinto, with consequent elimination of the disadvantages resulting therefrom such as enumerated above, the primer coatings or beads 9 of the lamp mount 4 are positioned as close as-possible to one another, within practicfl manufacturing limits, so as to-practically touch one another, as clearly shown in FIG. 2. In addition, the portions of the ignition filament 8 bridging and exposed between the primer beads or coatings 9 is'formed into an open loop shape, as clearly shown in FIG. 2, so as to have an appreciable amount of slack therein. For the purposes of the invention, the primer heads 9 are located so that their facinginner sides are spaced apart a distance b of less than 40 mils, and preferably as close as 15 to 25 *mils to one another,

at least at one region thereof between their innermost or heads 9 to the point where they practically touch one another, the field or area within which strands of the combustible material 2 are apt to be caught or trapped in the entrance opening between the primer beads and brought into con-tact with the ignition filament 8, during.

the insertion of the lamp mount 4 into the bulb 1 for sealing thereinto, is correspondingly reduced to a degree such' as to practically eliminate the likelihood of any such' strand entering the said opening between the primer'beads and contacting the ignition filament. Moreover, the formation of the ignition filament 8 into open loop shape be tween the primer beads 9 so as to have an appreciable amount of slack therein permits the filament, in most cases, to give way or yield to any pressure that may be:

exerted thereon by any strand of combustible material 2 thatactually may enter the space between the primer beads 9 during the insertion of the lamp mount 4 into the lam bulb 1, thereby minimizing the likelihood of such strand of combustible material contacting the igother words, 'a conventional ignition mount is first formed nition filament with sufiicient pressure to exert a materialcooling effect thereon or to cause an elongation and resultant severance of the filament during the energization thereof to set off the lamp.

The primer bead and ignition filament arrangement according to the invention may be conveniently produced simply by bending toward one another thelnner end portions of the lead-in wires of conventional coatings or beads 9 practically touch one another. In

in the customary manner by sealing a pair of lead-in wires 7 nto a glass support member such as the stem tube 5, with the inner tip ends of the lead-in wires located alongside one another and spaced apart a comparatively wide distance of at least 50 mils between their facing inner sides such as has been customary heretofore, and

then stretching a Wire filament straight across and connecting it to the inner tip ends of the lead-in wires so as to have an effective or lighted length therebetween V a few mils greater, i.e., 3 or so mils greater, than the said lead-in wire spacing. The primer coatings or beads 9 are then formed on the lead-in wires 7 by dipping the inner tip ends thereof and the ignition filament connected therebetween in a suspension of the primer material. After the coatings or beads 9 of primer material have dried on the lead-in wires, the inner end portions of the said wires are then bent or bodily shifted toward one another to reduce the spacing b between the primer heads 9 to a distance less than 40 mils, and preferably to the point where they nearly touch one another. It is desirable, however, not to bend the lead-in wires so far toward one another as to cause the primer beads 9 to actually contact each other, in order to avoid the possibility of the primer bead material being chipped or knocked off the lead-in wires. The bending together of the leadin wires 7 to close the gap between the primer beads 9 automatically causes the substantially taut filament 9 extending therebetween to buckle and transform itself into open loop shape so as to have the desired appreciable amount of slack therein. By forming the lamp mount structure 4 comprising the invention in the above described manner, the customary desired effective lighted filament length of between 50 to 65 mils, which has been determined to be the optimum length for proper ignition of flash lamps from the customary power sources employed for such purpose, is at the same time maintained.

Flash lamps provided with ignition mounts 4 constructed in accordance with the invention possess marked superiority in their flashability characteristics, and in their freedom from filament burn-outs without the lamps flashing. Thus, tests have conclusively shown that, for flash lamps having ignition mounts as heretofore constructed, the number of lamps that will fail to flash, when connected to a conventional electrical power source of approximately 1.1 amperes for a duration of 2 milliseconds circuit closure time, will ordinarily amount to around 30 lamps out of approximately 2400 lamps tested. In contrast thereto, in corresponding tests of identical type flash lamps except provided with ignition mounts 4 according to the invention, there were no failures to flash at all out of ap proximately 1100 lamps tested. Such complete elimination of all failures to flash when the lamps are connected to conventional electrical power supplies is, of course, a most important and highly desirable feature of the invention since it establishes the reliability or" the flash lamp to operate.

Although a preferred embodiment of my invention has been disclosed, it will be understood that the invention is not to be limited to the specific construction and arrangement of parts shown, but that they may be widely modified within the spirit and scope of my invention as defined by the appended claim. Thus, instead of the primer-carrying inner end portions of the lead-in wires 7 extending in the same general direction as the remainder of such wires so as to extend more or less lengthwise of the bulb axis, they may be bent over to extend transversely to the bulb axis as shown in my US. Patent 2,729,- 960, issued January 10, 1956 and assigned to the assignee of the present invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

The method of making a mount structure for flash lamps which comprises sealing a pair of lead-in wires into a glass support member to position end portions of said wires alongside one another and spaced apart a distance of at least mils, connecting a straight wire filament substantially taut across the said ends of said wires, applying coatings of primer material t the said ends of said Wires at their junctions with the filament, and then bending the said wires toward each other to close the space between the said end portions thereof to a distance less than 50 mils and the space between the primer coatings thereon to a distance less than 40 mils and form the portion of the filament extending between said primer coatings into open loop shape.

References Cited in the file of this patent UNITED STATES PATENTS 2,383,076 Pipkin Aug. 21, 1945 2,858,686 Roth Nov. 4, 1958 FOREIGN PATENTS 553,015 Canada Feb. 11, 1958 

